The PR_ATTACH_NUM property contains a number that uniquely identifies the attachment within its parent message.
| Header file: | MAPITAGS.H |
| Must be exposed by: | Attachment subobjects |
| Identifier: | 0x0E21 |
| Property type: | PT_LONG |
| Property tag: | 0x0E210003 |
Message stores generate and maintain the PR_ATTACH_NUM property. The attachment number is the secondary sort key, after the rendering position, in the attachment table.
PR_ATTACH_NUM is used to open the attachment with the IMessage::OpenAttach method. Within a client application's session, the PR_ATTACH_NUM property of a message attachment remains constant as long as the attachment table is open.
The message store propagates changes to the table using the IMessage::CreateAttach and IMessage::DeleteAttach methods. At its option the message store can generate table notifications on open attachment tables so that clients can resynchronize to those changes.